Process for producing lead free motor fuel

ABSTRACT

Refinery process stream containing isohexanes is converted to a suitable lead-free motor fuel by contact in the presence of steam with a tin-promoted noble metal-Group II aluminate catalyst.

United States Patent 91 [111 3,844,935

Drehman et a1. Oct. 29, 1974 PROCESS FOR PRODUCING LEAD FREE [56} References Cited MOTOR FUEL UNITED STATES PATENTS [75] inventors: Lewis E. Drehman; Floyd E. Farha, 3,003,949 10/1961 Hamilton 208/93 Jr., both of Bartlesville, Okla. 3,018,244 1/1962 3,320,155 5/1967 [73] Ass1gnee: Phillips Petroleum Company, 3,334,571 5/1968 Bartlesville, Okla. 3,649,520 3/1972 22 Filed: Jan.2, 1973 9 6/1972 [21] Appl. No.: 320,500 Primary ExaminerHerbert Levine 521 U.s.cl....- 208/79, 208/ 80, 208/93, [57] ABSTRMFT.

208/137,. 208/138 Refinery processv stream contammg isohexanes 15 con- 51] Int. Cl C10g 39/00 vetted a Sui-able lead'fee fuel by in [58] Field of Search 208/93 92 137 138 57 the presence of steam with a tin-promoted noble met- 208/65 6 4 6 al-Group II aluminate catalyst.

5 Claims, 1 Drawing Figure PROCESS'FOR PRODUCING LEAD FREE MOTOR FUEL This invention relates to hydrocarbon conversion processes. More particularly, the invention relates to the treatment of refinery process streams comprising isohexanes for the manufacture of high octane number motor fuels or motor fuel components.

The development and introduction by automotive engine manufacturers of high compression, high performance engines has required the petroleum industry to devote a considerable portion of its research efforts to the problem of discovering routes to high octane gasoline suitable for use as a motor fuel. As the performance characteristics of the engines increase, higher octane motor fuels'are required and slight variations in octane numbers become a critical parameter in an engines performance. For example, an octane difference in a motor fuel of as little as two to three numbers can be the difference between a quiet or a knocking engine. Historically, almost all of the routes currently used commercially depend to some extent upon the use of lead alkyls such as tetraethyl lead as additives to improve antiknock characteristics of gasolines. However, the demand for pure, unpolluted air has placed an emphasis on developing high octane gasolines that do not employ antiknock additives such as tetraethyl lead which can pollute the air when expelled with the engine exhaust.

lt is an object of this invention to provide a process for the conversion of hydrocarbon feedstocks.

It is a further object of this invention to provide a process for increasing the octane number rating of hydrocarbon feedstocks without the use of leadcontaining additives.

lt is another object ofthis invention to provide a process for producing high octane motor fuel or motor fuel components from low octane refinery process streams comprising isohexanes.

These and other objects, aspects and advantages of the invention will be apparent from the disclosure, claims and the attached drawing.

lt has been discovered that the octane number of refinery process streams comprising isohexanes can be substantially improved withoutthe necessity of adding lead-containing compounds such as tetraethyl lead by catalytic treatment of such streams in the presence of steam. Thus, the present invention provides a method whereby a refinery process stream comprising isohexanes can be converted to unleaded motor fuel or motor fuel components having an ASTM research octane number of at least 95.

The herein-described process provides a method of reforming refinery process streams to obtain products having a high octane number value. The process of this invention is particularly applicable in the treating of isohexanes-containing fractions, particularly such isohexanes-containing fractions obtained from refinery hexane isomerization units. Broadly, in accordance with the present invention, an isohexanes-containing stream is contacted in a reforming zone under reforming conditions with a Group Vlll metal or metal compound in combination with a tin-modified Group [I metal aluminate support to obtain aliquid hydrocarbon product having an ASTM research octane number of at least 95, said product being suitable as motor fuel or motor fuel blending stock.

More particularly, in accordance with the present invention, a virgin feedstock selected from the group consisting of natural gas liquids (NGL) and crude oil is treated by conventional refinery processes such as fractional distillation, hydrogenation. isomerization, and the like, to produce one or more liquid fractions containing, as a component thereof, isohexanes. Any or all of such refinery process streams can be treated in accordance with the process of this invention by contacting such stream(s) with steamin the presence of a particular catalytic material, which is described in greater detail hereinafter. The effluent from the catalytic treatment of the present invention will generally have an ASTM research octane number of at least and is suitable as a high octane number unleaded motor fuel or motor fuel blending stock.

More particularly, a virgin feed selected from the group consisting of natural gas liquids and crude oil is treated by conventional refining techniques to obtain a liquid fraction consisting essentially of hydrocarbons having six carbon atoms, said hydrocarbons comprising isohexanes, n-hexane, methylcyclopentane, cyclohexane and benzene. The fraction consisting essentially of hydrocarbons having six carbon atoms is fractionated to obtain a first fraction comprising hydrocarbons having six carbon atoms and boiling in the isohexane range; and a fraction comprising hydrocarbons having six carbon atoms boiling above the isohexane range. The fraction comprising hydrocarbons having six carbon atoms and boiling above the isohexane range is hydrogenated to provide an effluent comprising saturated hydrocarbons having six carbon atoms, which effluent is isomerized to convert n-hexane to isohexanes. The isomerization effluent is separated to obtain a second fraction comprising hydrocarbons having six carbon atoms and boiling in the isohexane range. The first and second fractions comprising hydrocarbon boiling in the isohexane range are reformed under reforming conditions in the presence ofa particularcatalyst system and steam to obtain a reformate having an ASTM research octane number of at least 95, suitable as a motor fuel or motor fuel blending stock.

The several treatment and fractionation zones, including the hydrogenation, isomerization, and reforming zones, wherein the fraction containing hydrocarbons having six carbon atoms and boiling above the isohexane range are treated to obtain a fraction comprising hydrocarbons boiling in the isohexane range, are known in the art and are operated at conventional conditions with known catalysts, where such materials are employed. Such zones and conditions will not be discussed herein in any detail.

It is a feature of the present invention that the reforming operation be effected in the presence of a particular steam-stable catalyst system. Thus, in accordance with this invention, the isohexanes-containing feed to the reforming zone is contacted under reforming conditions in the presence of steam and a steamstable catalyst selected from the group consisting of at least oneGroup Vlll metal or metal compound capable of reduction in combination with a tin-modified support selected from the group consisting of Group ll aluminates, particularlyGroup ll aluminate spinels, preferably zinc aluminate spinel. and mixtures thereof. The raw reformate is separated by conventional means to provide a reformate stream having an ASTM research octane number of .at least 95 which is suitable as a motor fuel or motor fuel blending stock.

The Group Vlll metals include nickel, platinum, ruthenium, palladium, iridium, or osmium, including compoundsof such metals which are capable of reduction, e.g., nickel nitrate, and including mixtures thereof.

The Group Vlll metal content of the catalyst should be in the range of about 0.1 to about 5 weight percent, preferably 0.1 to 1 weight percent, of the support. In addition to the Group Vlll metals, the catalyst composition can include activating components such as Group [A and [1A alkali metal and alkaline earth metal compounds as well as tin, germanium, and lead. Preferred catalysts are those which have the Group Vlll metal compound in combination with a tin compound deposited upon the tin-modified calcined support. The amount of tin in this embodiment is in the range of0.01 to 5 weight percent, preferably 0.01 to 1 weight percent, and is in addition to the amount of tin already incorporated into the tin-modified support. The tin component can be deposited with the Group Vlll components upon the catalytic carrier material of the invention separately or together by any manner known in the art such as by deposition from aqueous and nonaqueous solutions of tin halides, nitrates, oxalates, acetates, carbonates, propionates, nitrates, bromates, chlorates, oxides, hydroxides, and the like. For example, the tin compounds can be admixed in solution with the Group Vlll metal component and simultaneously deposited on the catalytic carrier, as from an aqueous solution of chloroplatinic acid and stannous chloride. Stannous halides are particularly effective and convenient as a source of tin. Thus, in accordance with the present invention, there is employed a catalyst support material selected from the group consisting of Group 11 aluminate spinels, and mixtures thereof, which have been modified by the incorporation therein of at least one tin compound prior to calcination of said support and deposition thereon of the Group Vlll metal catalytic material after calcination. Preferred supports include zinc aluminate spinel.

As noted, an essential feature of the invention is the use of a tin-modified support wherein the tin compound has been incorporated with the support material prior to calcination of the support. The tin compound can be added to the support material in a conventional manner such as by deposition from solution, ball mill mixing, volatilization, plasma spraying, and the like. When added to the support from solution, the tin compounds can be deposited from aqueous solution or from nonaqueous solvents such as alcohols, hydrocarbons, ethers, ketones, and the like. Regardless of the manner of application, the particular tin compound selected must have a capability of being convertible to either the stannous or stannic oxide form or to tin metal per se, as by conversion during calcination. Among the tin compounds which can be employed as the source for the tin or tin oxide in the support compositions of this invention are the halides, nitrates, oxalates, acetates, propionates, tartrates, hydroxides, and the like. The use of stannous halides is particularly effective and convenient. The tin compounds are added to the support material in an amount sufficient to incorporate therein from about 0.01 to 5 weight percent of tin, based on weight of finished support. Throughout the specification, the term weight percent of support" means parts by weight perlOO parts by weight of support. Preferably, the tin compound will be present in an amount in the range of 0.1 to about 2 weight percent, calculated as tin metal. Thus, subsequent to the incorporation of the tin and support material, the resulting intimate mixture is calcined for about 1 to hours at temperatures in the range of about 600 to about 2,500 F. Preferred supports are those prepared from calcining the support composites for about 2 to 50 hours at about 800 to about l,850 F.

Preferably, the reforming catalyst of the present invention should be nonacidic in nature and can be so made by treatment with sufficient alkali metal or alkaline earth metal compound or compounds in order to neutralize the acid sites of the catalyst composite including the metal and support in order to leave the deposit alkaline and to activate the catalyst for subsequent use in the reforming of isohexanes-containing feedstocks. The amount of alkali metal or alkaline earth metal compound or combinations of compounds can be determined experimentally; generally an amount in the range of 0.5 to 10 weight percent of the total'catalyst is effective.

Generally speaking, the Group Vlll metal compound and the adjuvant such as alkali metal or alkaline earth metal and/or tin compounds which are deposited on the tin-modified carrier to form the catalysts which are used in the reforming zone can be any compound in which the moieties, other than the desired catalyst components and oxygen, can be volatilized during heating or calcination. The catalytic materials can be sequentially combined with the support in any order or, for convenience, can be applied simultaneously in a single impregnation operation. After impregnation, the catalytic composites are preferably dried and can be calcined, if desired. The reforming operation of this invention is effected at temperatures in the range of about 800 to about 1,300 F., preferably in the range of about 950 to l,l00 F. Pressures are generally in the range of about atmospheric to 400 psig, preferably 75 to psig, and the space velocity is in the range of about 300 to 1,800 volumes of'feedstock per volume of catalyst per hour (GHSV), preferably in the range of 1,000 to 1,300. The reforming in accordance with the present invention is carried out in the vapor phase in the presence of steam and in the absence of oxygen at molar ratios of steam to isohexane-containing feedstock in the range of 2-3011, preferably 4l0:1. In the processes of the invention, when the ratios of steam to feedstock and pressures in the lower portion of the specified ranges are employed, the appropriate space velocities are preferably lower. Thus, for example,

when pressures in the range of 0-50 psig and the molar ratio of steam to feedstock is in the range of 2-1021, space velocity is preferably in the range of 300 to 1,000.

The accompanying drawing is a flow sheet of a process in which virgin feedstocks, such as natural gas liquids, and crude oil, are processed for the production of a high octane unleaded motor fuel or motor fuel blending stock in accordance with the present invention.

Referring to the drawing, virgin natural gas liquids and crude oil feedstocks are introduced through lines 1 and 6, respectively, into feedstock processing zones 50 and 60, respectively. Within processing zone 50, the natural gas liquids feedstock is separated into a first fraction comprising isopentane, n-pentane and lower boiling components, which fraction is withdrawn through line 2 and passed to further processing, not shown. A second and higher boiling fraction, comprising hydrocarbons having six or more carbon atoms, including isohexanes, n-hexane, methylcyclopentane, cyclopentane, benzene, n-heptane, isoheptanes and the like, is withdrawn from fractionation zone and passed through line 3 to fractionation zone 55. In fractionation zone 55, the stream comprising hydrocarbons having six or more carbon atoms is separated into a third stream comprisinghydrocarbons having seven or more carbon atoms, which is withdrawn through line 4 and passed to further processing, not shown, and a fourth stream consisting essentially of hydrocarbons having six carbon atoms and comprising isohexanes,

n-hexane, methylcyclopentane, cyclohexane, and benzene. The fourth stream consisting essentially of hydrocarbons having six carbon atoms which is withdrawn from fractionation zone is combined with a stream having the similar composition from crude oil processing and passed to fractionation zone 75. The virgin crude oil is processed in zone to obtain a light boiling fraction containing butane, isobutanes, and lighter components which is withdrawn from fractionation zone 60 through line 7 and passed to further processing, not shown. Additionally, from fractionation zone 60 is withdrawn a very high boiling topped crude stream through line 8 which is subsequently processed as well as intermediate distillate and gas-oil fractions taken off through lines 9 and 10. The intermediate fraction comprising hydrocarbons having at least five carbon atoms and having an end point in the range of about 400 F. is withdrawn through line 11 and passed to fractionation zone 65. In fractionation zone 65, the intermediate stream comprising hydrocarbons having at least five carbon atoms is separated into a tenth stream comprising isopentanes, normal pentanes and lighter boiling components which is withdrawn through line 12 and passed to further processing, not shown, and an eleventh stream comprising hydrocarbons having at least six carbon atoms and comprising isohexanes, normal hexane, methylcyclopentane, cyclopentane, benzene, isoheptanes, n-heptane, and the like, which is withdrawn through line 13 and passed to fractionation zone 70. In fractionation zone 70, the stream from fractionation zone comprising hydrocarbons having at least six carbon atoms is separated into a twelfth stream comprising hydrocarbons having more than seven carbon atoms and which is withdrawn through line 14, and a thirteenth stream consisting essentially of hydrocarbons having six carbon atoms and comprising isohexanes, n-hexane, cyclohexane, methylcyclopentane and benzene. The stream consisting essentially of hydrocarbons having six carbon atoms is withdrawn from fractionation zone through line 15 and combined with the stream consisting essentiallyof hydrocarbons having six carbon atoms from fractionation zone 55 and passed to fractionation zone 75. In fractionation zone 75, the combined streams consisting essentially of hydrocarbons having six carbon atoms are separated into a fourteenth stream consisting essentially of isohexanes which is withdrawn from fractionation zone and passed directly to reforming zone 99 by line 16. A fraction consisting essentially of nhexane, cyclohexane, methylcyclopentane and benzene is passed by line 17 to hydrogenation zone where the unsaturated aromatic compounds are h drogenated to the'corres'p'ondfn'g saturated li'ydfo'car ons.

. The effluent from hydrogenation zone 80 is passed by line 18 to isomerization zone where the n-hexane and methylcyclopentane are isomerized to isohexanes and cyclohexane, respectively. The effluent from isomerization zone 85 is passed by line 19 to fractionation zone where the stream is separated into a fraction consisting essentially of isohexane, which is withdrawn from fractionation zone 90 through line 20 and com bined with isohexane stream 16 from fractionation zone 75 and passed to reforming zone 99. A product stream from fractionation zone 90 comprising nhexane, cyclohexane, and methylcyclopentane is passed by line 21 to fractionation zone and separated into a cyclohexane fraction which is withdrawn from fractionation zone 95 through line 22 and'passed to storage; and a fraction containing n-hexane and methylcyclopentane, which is withdrawn from fractionation zone 95 and passed through line 23 to isomerization zone 85. The streams containing isohexanes are reformed in reforming zone 99 in the presence of steam over a Group VIII metal-tin-Group II aluminate catalyst and the raw reformate is separated by conventional means, e.g., fractional distillation, to provide a hydrocarbon product having an octane number inexcess of about 95, which product is removed from zone 99 through line 25 for subsequent use as a motor fuel or motor fuel blending stock. Hydrogen from zone 99 is passed to hydrogenation zone 80via line 24.-

The following'examples are illustrative of the invention. Example I demonstrates a method for preparing catalysts which are used in the reforming operation of this invention; Example II demonstrates reforming of an isohexane-containing feed stream in accordance with the invention.

EXAMPLE! y To ri idit 6r 5 1 grams of ma divided alumina in 270 ml of distilled water is added 43.5 grams of finely divided reagent grade zinc oxide and 1.2 grams of finely divided reagent grade stannic oxide. The mixture is stirred for approximately l5 minutes to form a stable homogeneous slurry. The slurry is dried overnight in a forced draft oven at C. After cooling, the dried support is sieved to 14-40 U.S. mesh and calcined in the air in a muffle furnace which is programmed as follows: 1 hour at 800 F., l hour at l,000 F., 1 hour at l,l00 F., and 3 hours at l,850 F. The thus-prepared support has a surface area of l l.5-l 1.8 meters /gram, a pore volume of 0.40 cc per gram and an apparent bulk density (ABD) of 0.70 gram per cubic centimeter. The support contains 27.6 weight percent alumina, 38.0 weight percent zinc and 1.0 weight percent tin.

The thus-prepared support was impregnated with platinum from an aqueous solution of chloroplatinic acid to form a catalyst composition containing 0.2 weight percent platinum, and dried at 300 C.

EXAMPLE II An ashaaie-caaaan iaea traiii ia'v'ag aboil ing range of l20l55 F. containing about 138 mol TABLE I ASTM Research Average Steamz- Octane Number Yield Reactor Reactor Inlet Space Velocitv Feed of Catalytic Rcformate, Temp. Pressure. Vol. feedlhr./- Mol Reformate. Volume F. psig Vol. of Catalyst Ratio clear I020 I 2.5l 6.7 95.9 90.2

Reformate shown in Table I is suitable as a motor fuel I 5' or motor fuel blending stock.

While certain embodiments of the invention have been described for illustrative purposes, the invention is not limited thereto. Various other modifications or embodiments of the invention will be apparent to those skilled in the art in view of this disclosure. Such modifications or embodiments are within the spirit and scope of the disclosure.

We claim:

1. A process for producing high octane number unleaded motor fuel stocks comprising:

processing refinery feedstocks selected from the group consisting of natural gas liquids and crude oil to obtain a first stream comprising liquid hydrocarbons having six carbon atoms;

fractionating said first stream to obtain a second stream comprising hydrocarbons having a boiling point in the isohexane range and a third stream comprising hydrocarbons having a boiling point above the isohexane range;

hydrogenating said third stream to obtain a fourth stream comprising saturated hydrocarbons having six carbon atoms;

isomerizing said fourth stream to obtain a fifth stream comprising isohexane and cyclohexane; fractionating said fifth stream to obtain a sixth stream comprising cyclohexane and n-hexane and a seventh stream comprising isohexane; contacting said second stream comprising hydrocarbons having a boiling point in the isohexane range and said seventh stream comprising isohexane in a reforming zone under reforming conditions in the presence of steam in the presence of a reforming catalyst selected from the group consisting of Group VIII metal in combination with a tinmodified Group ll metal aluminate; and separately recovering from said reforming zone a motor fuel blending stock having an ASTM research octane number of at-least 95.

2. A process according to claim 1 wherein said Group VIII metal is selected from the group consisting of nickel, platinum, ruthenium, palladium, iridium, osmium, and mixtures thereof.

3. A process according to claim 2 wherein said Group VIII metal is platinum.

4. A process according to claim 1 wherein said sixth stream is fractionated to obtain an eighth stream comprising n-hexane and said eighth stream is isomerized together with said fourth stream. I

5. A process according to claim 4 wherein said Group VIII metal is platinum and said Group ll metal aluminate is zinc aluminate.

=l= l =l l l 

1. A PROCESS FOR PRODUCING HIGH OCTANE NUMBER UNLEADED MOTOR FUEL STOCKS COMPRISING: PROCESSING REFINERY FEEDSTOCKS SELECTED FROM THE GROUP CONSISTING OF NATURAL GAS LIQUIDS AND CRUDE OIL TO OBTAIN A FIRST STREAM COMPRISING LIQUID HYDROCARBONS HAVING SIX CARBON ATOMS; FRACTIONATING SAID FIRST STREAM TO OBTAIN A SECOND STREAM COMPRISING HYDROCARBONS HAVING A BOILING POINT IN THE ISOHEXANE RANGE AND A THIRD STREAM COMPRISING HYDROCARBONS HAVING A BOILING POINT ABOVE THE ISOHEXANE RANGE; HYDROGENATING SAID THIRD STREAM TO OBTAIN A FOURTH STREAM COMPRISING SATURATED HYDROCARBONS HAVING SIX CARBON ATOMS; ISOMERIZING SAID FOURTH STREAM TO OBTAIN A FIFTH STREAM COMPRISING ISOHEXANE AND CYCLOHEXANE; FRACTIONATING SAID FIFTH STREAM TO OBTAIN A SIXTH STREAM COMPRISING CYCLOHEXANE AND N-HEXANE AND A SEVENTH STREAM COMPRISING ISOHEXANE; CONTACTING SAID SECOND STREAM COMPRISING HYDROCARBONS HAVING A BOILING POINT IN THE ISOHEXANE RANGE AND SAID SEVENTH STREAM COMPRISING ISOHEXANE IN A REFORMING ZONE UNDER REFORMING CONDITIONS IN THE PRESENCE OF STEAM IN THE PRESENCE OF A REFORMING CATALYST SELECTED FROM THE GROUP CONSISTING OF GROUP VIII METAL IN COMBINATION WITH A TIN-MODIFIED GROUP II METAL ALUMINATE; AND SEPARATELY RECOVERING FROM SAID REFORMING ZONE A MOTOR FUEL BLENDING STOCK HAVING AN ASTM RESEARCH OCTANE NUMBER OF AT LEAST
 95. 2. A process according to claim 1 wherein said Group VIII metal is selected from the group consisting of nickel, platinum, ruthenium, palladium, iridium, osmium, and mixtures thereof.
 3. A process according to claim 2 wherein said Group VIII metal is platinum.
 4. A process according to claim 1 wherein said sixth stream is fractionated to obtain an eighth stream comprising n-hexane and said eighth stream is isomerized together with said fourth stream.
 5. A process according to claim 4 wherein said Group VIII metal is platinum and said Group II metal aluminate is zinc aluminate. 